A cooling and heating simultaneous air-conditioning apparatus in which a relay unit and a plurality of indoor units are connected to an outdoor unit and which is capable of performing a cooling operation in which the operation mode of an operating indoor unit is cooling only, a heating operation in which the operation mode of an operating indoor unit is heating only, and a mixed (simultaneous) operation in which indoor units perform cooling and heating, is available (see, for example, Patent Literatures 1 to 3).
Patent Literature 1 describes a method for controlling the compressor frequency of the cooling and heating simultaneous air-conditioning apparatus and the heat exchange capacity of an outdoor heat exchanger.
Furthermore, Patent Literatures 2 and 3 describe a system in which an intermediate heat exchanger is provided in a relay unit and which performs a cooling and heating simultaneous operation in which heat transport from an outdoor unit to the relay unit is performed using a refrigerant, heat exchange between the refrigerant and brine in a refrigeration cycle is performed in the intermediate heat exchanger, and heat transport from the relay unit to an indoor unit is performed using the brine, and a control method on the water side.